Adsorption and oxidation of carbon monoxide on smooth palladium in sulfuric acid solution

Abstract

The adsorption of carbon monoxide was investigated on a smooth palladium wire electrode under steady-state conditions in 0.5 M H 2 SO 4 at room temperature. The coverage with carbon monoxide is equal to the saturation coverage between 0.2 and 0.65 V, measured vs. a hydrogen electrode in 0.5 M H 2 SO 4 . The surface of the palladium electrode is largely blocked for the dissolution of hydrogen inside the electrode at potentials of the α phase. The coverage decreases rapidly to zero in a narrow potential range above 0.65 V. The oxidation of chemisorbed carbon monoxide occurs in the absence of a noticeable coverage of oxygen atoms below 0.9 V. Above 0.9 V the oxidation CO ad is accompanied by the formation of the oxygen layer. The oxidation rate, determined at about half saturation coverage, follows a Tafel law at potentials below 0.9 V. The shape of voltammetric current-potential curves, measured in the presence of CO stirring, is interpreted on the basis of the adsorption results.